US20080298492A1 - Apparatus and Method for Estimating Channel in Communication System Supporting of Dm/Ofdma - Google Patents

Apparatus and Method for Estimating Channel in Communication System Supporting of Dm/Ofdma Download PDF

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Publication number
US20080298492A1
US20080298492A1 US12/158,304 US15830406A US2008298492A1 US 20080298492 A1 US20080298492 A1 US 20080298492A1 US 15830406 A US15830406 A US 15830406A US 2008298492 A1 US2008298492 A1 US 2008298492A1
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channel
data
phase change
phase
temporary
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US12/158,304
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Yong-Suk Hwang
Hyung-seob Kim
Kang-min Lee
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Posdata Co Ltd
Postdata Co Ltd
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Postdata Co Ltd
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Assigned to POSTDATA CO., LTD. reassignment POSTDATA CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KIM, HYUNG-SEOB, LEE, KANG-MIN, HWANG, YONG-SUK
Publication of US20080298492A1 publication Critical patent/US20080298492A1/en
Assigned to POSDATA CO., LTD. reassignment POSDATA CO., LTD. CORRECTIVE ASSIGNMENT TO CORRECT THE ASSIGNEE PREVIOUSLY RECORDED ON REEL 021137 FRAME 0211. ASSIGNOR(S) HEREBY CONFIRMS THE ASSIGNMENT. Assignors: KIM, HYUNG-SEOB, LEE, KANG-MIN, HWANG, YONG-SUK
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0204—Channel estimation of multiple channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
    • H04L25/023—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2668—Details of algorithms
    • H04L27/2673—Details of algorithms characterised by synchronisation parameters
    • H04L27/2675—Pilot or known symbols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT

Definitions

  • the present invention relates to an apparatus and a method for estimating a channel in a communication system supporting Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access (OFDM/OFDMA). More particularly, the present invention relates to an apparatus and a method for estimating a channel in a base station when using an Optional Partial Usage of Sub-Channels (OPUSC) mode in an uplink channel of a communication system supporting the OFDM/OFDMA.
  • OFDM/OFDMA Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access
  • a Wireless Broadband Internet which is Korean standard of the wireless portable Internet, applies Orthogonal Frequency Division Multiplexing (OFDM) for a signal transmission scheme to enable high-speed data service even in a state where the user is moving in the wireless environment. Additionally, Orthogonal Frequency Division Multiple Access (OFDMA) based on the OFDM is applied to enable a plurality of users to access the Internet simultaneously.
  • OFDM Orthogonal Frequency Division Multiplexing
  • OFDM Orthogonal Frequency Division Multiplexing
  • OFDMA Orthogonal Frequency Division Multiple Access
  • a transmitter inserts pilots in signals of the frequency domain when performing transmission.
  • the receiver performs channel estimation using the pilots in order to compensate distorted data existing among the pilots.
  • the channel can be estimated by averaging the pilots or by multiplying each pilot by a weight according to the position of the data and summing the multiplied values.
  • the OPUSC mode when used in the uplink channel of the OFDM/OFDMA communication system, a single pilot is included per tile. Therefore, it is hard to apply a certain method for averaging or interpolating the pilots. Furthermore, although the channel changes along a frequency axis in the frequency domain, the channel change is not easy to be estimated since the only one pilot can be used per tile.
  • the channel transmitting a signal in a frequency domain may be changed depending on a position of performing Fast Fourier Transform (FFT) with a received signal.
  • the channel in the frequency domain may be changed depending on a difference in time delay of signal being transmitted by multipath channels in a time domain.
  • FFT Fast Fourier Transform
  • the present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an apparatus and a method for estimating a channel in a communication system supporting Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access (OFDM/OFDMA) that uses an Optional Partial Usage of Sub-Channels (OPUSC) mode in an uplink channel.
  • OFDM/OFDMA Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access
  • OUSC Optional Partial Usage of Sub-Channels
  • an apparatus for estimating a channel in a communication system supporting Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access (OFDM/OFDMA) using an Optional Partial Usage Sub-Channel (OPUSC) mode comprising a Radio Frequency (RF) module for converting RF band signals received via antenna to low-frequency band signal; a Fast Fourier Transform (FFT) module for converting time-domain signal of the low-frequency band to frequency-domain signal; a derandomizer for performing derandomization with respect to the frequency-domain signal by using a random sequence used by a transmitter; a depermutation module for performing depermutation to collect tiles of the subchannel transmitted on different sub-carriers output from the derandomizer; and a channel estimation module for extracting pilots and data from the respective tiles of the sub-channel, estimating phase change using the extracted pilots and data, and obtaining a channel estimation value by compensating the estimated phase change.
  • RF Radio Frequency
  • FFT
  • a module for estimating a channel in a communication system supporting OFDM/OFDMA using an OPUSC mode comprising: a phase change estimation unit for extracting pilots and data included in an input signal, and estimating phase change using the extracted pilots and data; and a phase reflection unit for obtaining a channel estimation value by reflecting the phase change estimated by the phase change estimation unit.
  • a method for estimating a channel in a communication system supporting OFDM/OFDMA using an OPUSC mode comprising the steps of: a) converting RF band signals received via antenna to low-frequency band signal; b) converting time-domain signal of the low frequency band to frequency-domain signal; c) derandomizing the frequency-domain signal based on using a random sequence used by a transmitter; d) collecting tiles of the sub-channel for derandomized signal being transmitted on different sub-carriers; e) extracting pilots and data from the respective tiles of the sub-channel, and estimating phase change using the extracted pilots and data; and f) obtaining a channel estimation value by reflecting the estimated phase change.
  • a method for estimating a channel in a communication system supporting OFDM/OFDMA using an OPUSC mode comprising the steps of: a) extracting data and pilot included in respective tiles of the signal input by the sub-channel; b) obtaining a temporary channel estimation value using the extracted pilots; c) compensating the channel of the data using the temporary channel estimation value, and determining a temporary phase information value with respect to the channel-compensated data; d) compensating the phase information of the data by the temporary phase information value; and e) estimating the phase change based on the phase-information-compensated data.
  • phase change estimated by a channel estimation module using pilots and data is compensated in a channel compensation module.
  • phase change of a received signal caused by time delay can be removed.
  • phase change can be achieved by estimating the phase change by the sub-channel.
  • FIG. 1 is a structural view of a logical signal being transmitted when an Optional Partial Usage of Sub-Channels (OPUSC) mode is used in an uplink channel of a communication system supporting Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access (OFDM/OFDMA);
  • OPFDM/OFDMA Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access
  • FIG. 2 is a structural view of a channel estimation apparatus applied to the communication system supporting the OFDM/OFDMA according to an embodiment of the present invention
  • FIG. 3 is a detailed structural view of a channel estimation module of FIG. 2 ;
  • FIG. 4 is a detailed structural view of a phase change estimation unit of FIG. 3 ;
  • FIG. 5 is a structural view of a tile used in the OPUSC mode.
  • FIG. 6 is a flow chart explaining a method for estimating a channel in the communication system supporting OFDM/OFDMA according to an embodiment of the present invention.
  • Channel estimation apparatus and method according to the present invention are applicable to a receiver and a transceiver.
  • channel estimation is performed in a communication system supporting Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access (OFDM/OFDMA) that uses an Optional Partial Usage of Sub-Channels (OPUSC) mode in an uplink channel.
  • OFDM/OFDMA Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access
  • OPS Optional Partial Usage of Sub-Channels
  • FIG. 1 shows a logical structure of a signal being transmitted when using the OPUSC mode in the uplink channel, in the communication system supporting the OFDM/OFDMA.
  • one sub-channel comprises 8 tiles and each tile comprises 1 pilot and 8 data.
  • Each sub-channel covers 3 OFDMA symbols.
  • the logical signal is loaded and transmitted on respectively different sub-carriers respectively different in the tile.
  • the channel estimation apparatus comprises a Radio Frequency (RF) module 210 , a Fast Fourier Transform (FFT) module 220 , a derandomizer 230 , a depermutation module 240 , a channel estimation module 250 , and a channel compensation module 260 .
  • RF Radio Frequency
  • FFT Fast Fourier Transform
  • the RF module 210 converts RF band signals received via antenna to low-frequency band signal.
  • the FFT module 220 converts the low-frequency band signal of a time domain to a frequency domain signal.
  • the derandomizer 230 performing derandomization with respect to the frequency-domain signals converted by the FFT module 220 , by using a random sequence used by a transmitter when transmitting the RF band signals.
  • the depermutation module 240 collects, by the sub-channel, the tiles transmitted along with the respectively different sub-carriers.
  • the signal collected by the sub-channel is input to the channel estimation module 250 .
  • An estimated value in the channel estimator 250 is input to the channel compensation module 260 to be used in compensating the channel.
  • the signal input to the channel estimation module 250 is processed by the sub-channel.
  • the tiles constituting the sub-channel are transmitted along with respectively different sub-carriers. Accordingly, time delay is incurred and a phase change is caused on the respective sub-carriers. According to the present invention, channel estimation can be achieved by estimating the phase change.
  • the present invention will be described mainly about the channel estimation module 250 , while omitting explanation of generally known elements.
  • the channel estimation module 250 to estimate the channel in the OFDM/OFDMA communication system using the OPUSC mode in the uplink channel comprises a phase change estimation unit 300 and a phase reflection unit 400 .
  • the phase change estimation unit 300 extracts pilots and data from signals input by the sub-channel, and estimates phase change that increases and decreases along a frequency axis, by the sub-channel.
  • the phase reflection unit 400 reflects the estimated phase to the pilots.
  • FIG. 4 is a detailed view showing the structure of the phase change estimation unit 300 of FIG. 3 .
  • the phase change estimation unit comprises a data extractor 310 , a pilot extractor 320 , a determiner 330 , and a phase calculator 340 .
  • the transmitted sub-channel comprises 8 tiles.
  • Each tile has a 3 ⁇ 3 matrix structure comprising 1 pilot P in the center and 8 data (d nk ; d 11 , d 12 , d 13 , d 21 , d 23 , d 31 , d 32 , d 33 ) symmetrically surrounding the pilot.
  • One sub-channel covers 3 OFDM symbols.
  • each sub-carrier has a phase change due to time delay ⁇ .
  • the data extractor 310 extracts the data d nk from the signalinput by the sub-channel, and outputs the extracted data d nk (S 610 ).
  • the data can be expressed by [Equation 1] as below:
  • the pilot extractor 320 extracts the pilot signal P i from the input signal (S 610 ).
  • the pilot can be expressed, for example, by [Equation 2] as below:
  • the pilot extractor 320 obtains a temporary channel ‘h_hat’ using the extracted pilot P i (S 620 ).
  • a temporary channel estimation value ‘h_hat’ can be obtained by [Equation 3] as below:
  • each data includes phase information of the data ⁇ nk (data value) and phase change ⁇ ⁇ by the time delay.
  • the phase information of the data representing the data value is removed first. In other words, data components are removed from each data signal. And then, the phase change ⁇ ⁇ by the time delay is estimated.
  • the determiner 330 temporarily determines a phase information value with respect to the data compensated by the temporary channel estimation value ‘h_hat’ (S 640 ).
  • the temporary data phase information value is determined according to the modulation method.
  • compensated output value b nk can be expressed by [Equation 4] as below:
  • the phase change calculator 340 estimates the remaining phase change by the time delay. More specifically, the phase change calculator 340 performs conjugation-multiplication with data located on the frequency axis, and accumulates the result value.
  • the phase difference between two sub-carriers 510 and 530 ( FIG. 5 ) is obtained by performing arctan-operation, for example.
  • An average phase change is obtained by dividing the phase difference by 2 (S 660 ).
  • ‘2’ the multiplying number, denotes positional difference between the sub-carriers.
  • data d 11 belonging to the sub-carrier 510 and data d 21 belonging to a sub-carrier 520 are distanced from each other by 1 sub-carrier.
  • the data d 11 of the sub-carrier 510 and data d 31 of the sub-carrier 530 are distanced from each other by 2 sub-carriers.
  • Equation 5 expresses the result value of the phase change estimation unit 300 through the above procedures, as follows:
  • the phase reflection unit 400 reflects the phase change ⁇ ⁇ by the time delay to the pilot P i extracted by the phase change estimation unit 300 , thereby obtaining a channel estimation value for compensating data (S 670 ). Data included in the same sub-carrier in one tile are compensated using the same channel estimation value.
  • the channel estimation value of the sub-carrier for compensating data is determined in the following manner.
  • the channel estimation value corresponding to the first sub-carrier is P i ⁇ exp( ⁇ j ⁇ ), the second sub-carrier is P i ⁇ 1, and the third sub-carrier is P i ⁇ exp(j ⁇ ).
  • the channel estimation value is transmitted to the channel compensation module 260 .
  • the channel compensation module 260 reflects the channel estimation value to the signal output from the depermutation module 240 , accordingly compensating the channel (S 680 ).

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Power Engineering (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Radio Transmission System (AREA)
US12/158,304 2005-12-31 2006-12-29 Apparatus and Method for Estimating Channel in Communication System Supporting of Dm/Ofdma Abandoned US20080298492A1 (en)

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KR1020050136295A KR100718592B1 (ko) 2005-12-31 2005-12-31 Ｏｆｄｍ/ｏｆｄｍａ 방식을 지원하는 통신 시스템의 채널추정 장치 및 방법
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Cited By (8)

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US20060248376A1 (en) * 2005-04-18 2006-11-02 Bertan Tezcan Packet processing switch and methods of operation thereof
US7693040B1 (en) * 2007-05-01 2010-04-06 Integrated Device Technology, Inc. Processing switch for orthogonal frequency division multiplexing
US7706387B1 (en) 2006-05-31 2010-04-27 Integrated Device Technology, Inc. System and method for round robin arbitration
US20100110874A1 (en) * 2008-10-20 2010-05-06 Lg Electronics Inc. Method and apparatus for transmitting signal in a wireless communication system
US20100111014A1 (en) * 2008-10-20 2010-05-06 Lg Electronics Inc. Method and apparatus for transmitting signal in a wireless communication system
US7747904B1 (en) 2006-05-12 2010-06-29 Integrated Device Technology, Inc. Error management system and method for a packet switch
US7817652B1 (en) 2006-05-12 2010-10-19 Integrated Device Technology, Inc. System and method of constructing data packets in a packet switch
US20110296270A1 (en) * 2010-05-28 2011-12-01 Samsung Electronics Co., Ltd. Apparatus and method for resource segmentation in wireless communication system

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US20110038403A1 (en) * 2000-06-14 2011-02-17 Nec Corporation Orthogonal frequency division multiplex modem circuit

Patent Citations (1)

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US20110038403A1 (en) * 2000-06-14 2011-02-17 Nec Corporation Orthogonal frequency division multiplex modem circuit

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060248377A1 (en) * 2005-04-18 2006-11-02 Bertan Tezcan Packet processing switch and methods of operation thereof
US7684431B1 (en) 2005-04-18 2010-03-23 Integrated Device Technology, Inc. System and method for arbitration in a packet switch
US20060248376A1 (en) * 2005-04-18 2006-11-02 Bertan Tezcan Packet processing switch and methods of operation thereof
US7882280B2 (en) * 2005-04-18 2011-02-01 Integrated Device Technology, Inc. Packet processing switch and methods of operation thereof
US7739424B2 (en) 2005-04-18 2010-06-15 Integrated Device Technology, Inc. Packet processing switch and methods of operation thereof
US7747904B1 (en) 2006-05-12 2010-06-29 Integrated Device Technology, Inc. Error management system and method for a packet switch
US7817652B1 (en) 2006-05-12 2010-10-19 Integrated Device Technology, Inc. System and method of constructing data packets in a packet switch
US7706387B1 (en) 2006-05-31 2010-04-27 Integrated Device Technology, Inc. System and method for round robin arbitration
US7693040B1 (en) * 2007-05-01 2010-04-06 Integrated Device Technology, Inc. Processing switch for orthogonal frequency division multiplexing
US20100111014A1 (en) * 2008-10-20 2010-05-06 Lg Electronics Inc. Method and apparatus for transmitting signal in a wireless communication system
US20100110874A1 (en) * 2008-10-20 2010-05-06 Lg Electronics Inc. Method and apparatus for transmitting signal in a wireless communication system
US8130714B2 (en) * 2008-10-20 2012-03-06 Lg Electronics Method and apparatus for transmitting signal in a wireless communication system
US8254247B2 (en) 2008-10-20 2012-08-28 Lg Electronics Inc. Method and apparatus for transmitting signal in a wireless communication system
US20110296270A1 (en) * 2010-05-28 2011-12-01 Samsung Electronics Co., Ltd. Apparatus and method for resource segmentation in wireless communication system
US9621302B2 (en) * 2010-05-28 2017-04-11 Samsung Electronics Co., Ltd. Apparatus and method for resource segmentation in wireless communication system

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